My proposed research seeks to address specific gaps in our understanding of how nervous systems modulate transitions among complex motor behaviors. Specifically, although considerable information is available regarding the neuromuscular control of stereotyped movements such as walking or running, little is known about how the nervous system regulates muscles to change speed, alter direction, and maneuver, I will examine these questions using the flight behaviors of hummingbirds. Hummingbirds are particularly good organisms for studies of motor control because of their extreme design for precise locomotion and maneuvering as well as their ease of training to complex flight behaviors. The approach of this study is to conduct two sets of laboratory experiments that quantify muscle activity and performance. During free flight I will record the wing and body motions (kinematics) using high-speed videography and measure the muscle activity of the 17 flight muscles using electromyography (EMG). Having linked muscle activity to flight kinematics I will then measure muscle forces on detached muscles using work loops to quantify how muscle stimulation patterns correspond to power production. Linking detailed flight kinematics, in vivo EMG recordings, and in vitro work loop analysis will provide an integrated view of all of the important characteristics of the motor control of shifts in locomotor modes. Improved understanding of the neural control of the regulation of complex motor behaviors would have direct relevance to studies of human motor control diseases and motor control degeneration that accompanies ageing. [unreadable] [unreadable]